I/O Modules

Description

Input/Output modules (I/O modules) are interface cards where data is transferred to accomplish a function. They receive input data from sensors, transducers or programmable logic controllers (PLC) and send output data to other devices in system. I/O modules comprise I/O logic (module between CPU and I/O module), data lines (for data transfer between system bus and I/O module) and input/output interface (to control device operation).

Functions

Major functions of I/O modules are:

• Control and timing
• Processor communication
• Device communication
• Data buffering
• Error detection

Types

Types of I/O modules are classified as:

• Analog I/O modules
• Digital I/O modules
• PCI I/O modules

Advantages

I/O modules are needed to overcome certain problems when:

• there is a mismatch between CPU and peripherals speed it is improper to use slow peripheral on a high speed system bus
• numerous peripherals are to be connected to a single system bus but it is highly difficult as flexibility is reduced
• the peripherals data format differ from that of CPU format

I/O modules have data buffering capability to remove mismatch between speed of peripherals and CPU, and in built error detector mechanism for checking mechanical and communicational errors.

Applications

I/O modules work as a mediator between I/O devices and CPU. To monitor temperature in wood drying kiln and to measure water from pump analog I/O modules are used. Solid-state I/O modules are used to switch AC as well as DC loads and also sensing AC and DC control voltages for controlling input to PLC. They are also used in conjunction with computers and computer processors for data acquisition and also for measuring complex signals. Some I/O modules combine the function of multiple I/O cards on single I/O card. Attaching a PCI I/O card to a computer gives it an extra port for printers, scanners etc.